A piezoelectric/electrostrictive membrane type sensor can be used for measuring fluid characteristics such as viscosity, density and concentration by use of the electromechanical converting function of a piezoelectric/electrostrictive element in which a membrane-like piezoelectric/electrostrictive body disposed in the sensor is sandwiched between a pair of electrodes. For example, when the piezoelectric/electrostrictive membrane type sensor (the piezoelectric/electrostrictive element) is vibrated in a fluid, a mechanical resistance is received by the viscosity resistance of the fluid, and the electric constant of the piezoelectric/electrostrictive element changes in a constant relationship with respect to the mechanical resistance. Therefore, the sensor can detect these changes in constant relationship to measure the viscosity of the fluid. It is to be noted that any prior document having the same theme as or a theme in common with the following theme of the present invention does not seem to be present, but examples of a prior document for reference of the piezoelectric/electrostrictive membrane type sensor include Patent Documents 1 to 4.
Patent Document 1: JP-A-8-201265
Patent Document 2: JP-A-5-267742
Patent Document 3: JP-A-6-260694
Patent Document 4: JP-A-2005-164495